Quick overview from the supplier:
MB AM4 ASRock B550 PRO4 ATX
// CPU
- Supports AMD AM4 Socket Ryzen™ 3000, 3000 G-Series, 4000 G-Series, 5000 and 5000 G-Series Desktop Processors*
Chipset
- AMD B550
Memory
- Dual Channel DDR4 Memory Technology
- 4 x DDR4 DIMM Slots
- Supports DDR4 4733+ (OC)
- Max. capacity of system memory: 128GB**
Graphics
- Integrated AMD Radeon Vega Series Graphics in Ryzen Series APU*
- Shared memory default 2GB. Max Shared memory supports up to 16GB.**
- Dual graphics output: support HDMI and D-Sub ports by independent display controllers
- Supports HDMI 2.1 with max. resolution up to 4K x 2K (4096x2160) @ 60Hz
- Supports D-Sub with max. resolution up to 1920x1200 @ 60Hz
Audio
- 7.1 CH HD Audio with Content Protection (Realtek ALC1200 Audio Codec)
LAN
- PCIE x1 Gigabit LAN 10/100/1000 Mb/s
- Realtek RTL8111H
Slots
- 2 x PCI Express x16 Slots (PCIE1: Gen4x16 mode; PCIE3: Gen3 x4 mode)*
- 2 x PCI Express 3.0 x1 Slots
- 1 x M.2 Socket (Key E), supports type 2230 WiFi/BT PCIe WiFi module
Storage
- 6 x SATA3 6.0 Gb/s Connectors, support RAID (RAID 0, RAID 1 and RAID 10), NCQ, AHCI and Hot Plug*
- 1 x Hyper M.2 Socket (M2_1), supports M Key type 2260/2280/22110 M.2 PCI Express module up to Gen4x4 (64 Gb/s) (with Matisse) or Gen3x4 (32 Gb/s)
- 1 x M.2 Socket (M2_3), supports M Key type 2242/2260/2280 M.2 SATA3 6.0 Gb/s module and M.2 PCI Express module up to Gen3 x2 (16 Gb/s)**
USB
- 1 x USB 3.2 Gen2 Type-A Port (10 Gb/s) (Supports ESD Protection)
- 1 x USB 3.2 Gen2 Type-C Port (10 Gb/s) (Supports ESD Protection)
- 4 x USB 3.2 Gen1 Ports (Supports ESD Protection)
- 2 x USB 2.0 Headers (Support 4 USB 2.0 ports) (Supports ESD Protection)
- 1 x USB 3.2 Gen1 Header (Supports 2 USB 3.2 Gen1 ports) (Supports ESD Protection)
https://www.asrock.com/mb/AMD/B550%20Pro4/index.asp#Overview
